Prevent a theoretical segfault.
Prevent a theoretical segfault.

* subversion/libsvn_client/mergeinfo.c
  (elide_mergeinfo): End a call to svn_dirent_join_many() with NULL.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@878420 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion